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<h2><a name="SECTION0051140000000000000000"></a><a name="typesmethods"></a>
<br>
3.11.4 Methods 
</h2>
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<p>
Methods are functions that are called using the attribute notation.
There are two flavors: built-in methods (such as <tt class="method">append()</tt> on
lists) and class instance methods.  Built-in methods are described
with the types that support them.

<p>
The implementation adds two special read-only attributes to class
instance methods: <code><var>m</var>.im_self</code> is the object on which the
method operates, and <code><var>m</var>.im_func</code> is the function
implementing the method.  Calling <code><var>m</var>(<var>arg-1</var>,
<var>arg-2</var>,  ..., <var>arg-n</var>)</code> is completely equivalent to
calling <code><var>m</var>.im_func(<var>m</var>.im_self, <var>arg-1</var>,
<var>arg-2</var>,  ..., <var>arg-n</var>)</code>.

<p>
Class instance methods are either <em>bound</em> or <em>unbound</em>,
referring to whether the method was accessed through an instance or a
class, respectively.  When a method is unbound, its <code>im_self</code>
attribute will be <code>None</code> and if called, an explicit <code>self</code>
object must be passed as the first argument.  In this case,
<code>self</code> must be an instance of the unbound method's class (or a
subclass of that class), otherwise a <tt class="exception">TypeError</tt> is raised.

<p>
Like function objects, methods objects support getting
arbitrary attributes.  However, since method attributes are actually
stored on the underlying function object (<code>meth.im_func</code>),
setting method attributes on either bound or unbound methods is
disallowed.  Attempting to set a method attribute results in a
<tt class="exception">TypeError</tt> being raised.  In order to set a method attribute,
you need to explicitly set it on the underlying function object:

<p>
<div class="verbatim"><pre>
class C:
    def method(self):
        pass

c = C()
c.method.im_func.whoami = 'my name is c'
</pre></div>

<p>
See the <em class="citetitle"><a
 href="../ref/ref.html"
 title="Python Reference Manual"
 >Python Reference Manual</a></em> for more
information.

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